Past studies have shown that oral or nasal application of tolerogens can induce peripheral tolerance, and these methods have been successfully used for treatment of allergies. One limitation of such approaches is relatively large amounts of materials are often needed to successfully tolerize the host. To enable a more efficient method to deliver tolerogens, we have devised a single dose method to induce oral or nasal tolerance to stimulate the induction of regulatory T cells. Previous studies have shown that M cells on mucosal inductive tissues are required for oral tolerance, and in the absence of Peyer's patches, tolerance cannot be induced. Thus, we hypothesized that targeting mucosal inductive tissues is important for tolerance induction. Using an M cell ligand to test this hypothesis, proteins genetically fused to the adhesin or hemagglutinin protein from reovirus serotype 3, protein s1 (ps1), tolerize the host. Our data show that oral or nasal application of the fusion protein, ovalbumin (OVA)-ps1, stimulates T and B cell unresponsiveness to OVA. Given these findings, we hypothesize that ps1 delivered autoantigens can induce tolerance and is sialic acid binding-dependent, and tolerance is facilitated via apoptosis of target cells and, possibly, local antigen-presenting cells (APCs), which in turn are ingested by other APCs. To enable this effort, studies in Specific Aim 1 will show ps1 requires M cells and/or sialic acid (SA) to enable tolerance induction. Studies in Specific Aim 2 will show that ps1 mediates tolerance induction via apoptosis of APCs and/or epithelial cells. Studies in Specific Aim 3 will show that prophylatic versus therapeutic mechanisms of protection mediated by ps1 differ in its dependency on adaptive and innate immune cells. PUBLIC HEALTH RELEVANCE: Induction of tolerance to auto-antigens is often compromised by repeated or large dosages of auto- antigens to stimulate T cell unresponsiveness. Herein this application, we have identified an adapter molecule to which proteins can be genetically fused and when applied mucosally, tolerance can even be induced with a single dose. The overall goals of this work will be to develop a simple method and carrier for eliciting tolerance and to design a regimen that can prevent and/or treat autoimmune diseases or allergies of the oral cavity and salivary glands. The prevalence of Sj"gren's Syndrome is estimated at 2-4 million individuals, which represents the second leading autoimmune rheumatic disease in the US. This disease is nearly ten times more prevalent in females than males. Recent data suggests that Sj"gren's Syndrome has a regulatory T cell component to limit disease. Thus, once we are able to establish the ps1 delivery technology, we will move forward to use current models for Sj"gren's Syndrome to test if disease progression can be reduced.